The importance of variable chewing patterns for the preservation of the masticatory system structure

Masticatory movements are characterized by variability. Although chewing patterns vary depending on the type and position of the food being eaten, individual-specific features can be observed. This study comprised computerassisted tracking and analysis of jaw muscle activity during standardized chewing activity using the Jaw Motion Analyzer (JMA), an ultrasonic measurement system, in conjunction with JawReports software, developed at the University of Greifswald. This study's findings show that temporomandibular dysfunction (TMD) has a significant impact on the variability of chewing patterns. The healthier the masticatory system, the more variable the chewing patterns, and the more impaired the system, the more monotonous and stereotyped the patterns become. The same applies to lateral preference in mastication. Mastication may take place on both sides of the mouth at the same time (simultaneous bilateral), may switch back and forth between the right to the left side of the mouth (alternating bilateral), or may occur preferentially on either the right or the left side of the mouth (unilateral chewing). Alternating bilateral mastication can be classified as "normal," because unilateral mastication is less effective and can be associated with dysfunctions. Lateral preference in mastication is associated with unilateral facial muscle pain, unilateral temporomandibular joint pain, and unilateral clicking sounds. Furthermore, there is a highly significant association between chewing side preference and asymmetrical loss of antagonist contact and specific types of dentures. Regarding relative risk, the odds of having a preferred chewing side were significantly higher in individuals with plastic removable partial dentures (RPDs) with wrought wire clasps and attachment-retained RPDs, than in those with fixed partial dentures, telescopic dentures and full dentures. Any type of monotonous jaw movement is likely to cause repetitive stereotyped movements and detrimental occlusal forces, resulting in increased wear of anatomical structures. Appropriate measures to prevent these problems and to promote the variability of chewing patterns will be discussed in this article. Keywords: chewing movement, dysfunction of stomat-ognathic system, variability of occlusal movements, chewing side preference